Recovery of zinc as sulphate from dross



Nov. 2 1926.

J. O.' BETTER-FON RECOVERY OF ZINC AS SULPHATE FROM` DROSS Original Filed'June 28, 192;',

2 Sheets-Sheet 1 IN I/ENTORy am ATTORNEY Nov. 2 1926.

J. O. BETTERTON RECOVERY OF ZINC AS SULPHAQIE FRO M lDROSS 2 Sheets-Sheet 2 Original Filed June 28 k@ mluww QU ihu LUMQ 1N VENTGR 0m MM @m 'ATTORNEY :so forni olf' practicing iny iinontion, and the rine contents. The result would be the .35 Figure l is a iiow' sheet otithe several. therefore not come into commercial use.

Etiit't DE .Ze ME SULFHA'EE FROM DRGS.

Application .flied .time 28, 5h23, Serial No. esame. Renewed .prl 2d, i926.

llfhis 'invention relates to the art oi inetal has no reference to this welhlnown process, recovery, and hes particular reference to only so much of the flow sheet relating improvements in recoveringA zinc sul thereto being shown es is necessary to .an phatefatroni the dross produced in melting understanding of the invention. The ina eine, f 'rention refers particularly to the treatment 55 The prese invention has for its :main oi' the dross produced in the melting; re* object the utilization ot materials heretotort l() and 'which may he removed there nfore whollyor payrtly wasted. in accord irorn at desired times. it has been found ance with this object a practicable method to consist mainly of oxidized zinc, some Inelo irs-provided in which :there is substantially tallie .eine and chlorides. 6u no chlorine left inthe zinc solution recovered In order that the present invention may to interfere y'with the succo' 'ful operation of be better understood, a brief description y the eiectrolytic coll in vwinch the recovered will. he given oi the. processes heretofore zinc solution is placed to deposit the Zinc. unsuccessfully employed inthe attempt to i5 @ther objects relate to lthe recovery of recover the valuable constituents of the 65 the flux used in the process so that the op dross removed from the nietal'hath. Such eration is cyclicJ onli7 enough of the flux processes have included rfi-treatment of the being added to the initial charge to compen dross with further additions of sai-ainsatc lor haiulln r io. I ,i reduction oit noniac, hut even with the exercise of the 2li the oi ir and maintenance. utmost care, et least 11% of the original '"o oi? a plant i'or the reco of valuehle weight oi? cathode deposit will still reinain metals to a minimum; and to ozridiaation. oif' as .tina'l dross. Upon. attemptingr to 'reach me cai-hon particle:- e Carson was used this final dross with liquid containing di- 'in the o ,'inal nielt of', the zinc strippings. lute suiphuri'o acid, it has been Yfound that ifm-i0 mh@ Objects and advantages of 'the resulting solution, althoughit contains 75 on will he in rt @hvimis trein much of the zinc left in the final. dross in an inspectionofthe :ficconipanjiing drawings solution, cannot he added to the solution and iii part will iore. fully set forth in which is used for replenishingg` the electrolyte the 'following particular x: lotion of one ot the eieotrolytic cells because of the .chloinvention also conA s in certain new and 'fouling of the 'whole cell with chlorides, novel. features hereinafter set forth and and the electrolytic deposition of the zinc claimed. could not be satisfactorily accomplished lu the accorn ianying drawings., With lead anodes. Such prior methods have sa steps ot one process embodying eatures of According to the present invention the the invention; dross is screened ina suitable screen 20, liigorc i?, is a flow sheet oil'. the several and the oversize screenings returned to the 'stops ot an alternative process embodying inciting retort l0 by -Wav 'of' path 2l and features of thc invention. charged into the next melt of cathode zinc "referring to Figure i, there is shown in deposit. i have found a so-ealled six-rnesli` diagrammatic forni a usual. melting retort screen suitable for the purpose. The dross 1li of a zinc reh'nery into which there is passing these-reen is calcined at a red heat introduced cathode deposit indicated at ll. in a suitable inutile, roasting or calcining and from which there is a. yield ot metallic furnace 2:2 of Well-lmown construction. zinc indicati-zd at l2, usually ist greater This serves to voiatilize the chlorine confiom about 90% hy Weight oi' the cathode tents of the dross mainly as volatile metallic deposit melted down. in initial charge of chlorides, which arev readily recovered hy ilus such. as salnnunoniac indicated at v13 is the use oi' an. ordinary fan Q3 -for main 51 added to toe retort, The present invention taining a small movement of gases through 100 this point forward similar scribed for Figure l. and requires no fur- (ifi sulphuric acid, and

the `furnace 22,' followed hy passing or conduetii'ng4 the sulilimcd chlorides to a condensiup chamber 24, through. a comluctinp,` passage 25. The chlorine contents are volatilized. and any'ne particles ot metallic zinc are oxidized, as are also any carhon particles in case carbon was used in the original melt of z/.inc stripping'. Fl`he gaseous oxides of carbon pass oliA with the other volatile matter. The chlorides recovered in this manner are returnedover a path 9.6 to the melting' retort l0, for use a lux with a'succeeding melt of cathode zinc, replac ing an equal amount of fresh salnmnoniac supplied over the path i3, which would otherwise be required. The non-condensible gases escape through exit openings pro vided for the purpose, preferably to and through a stack. :if desired the gases from the condensingr chamber may he directed through bags, in order to insure practically complete recovery of all the volatile chlorides.

It. is to be understood that inthe vola.

tilizing and condensing of the chlorides that suhstantially all ot the zine chloride is always condensed in the vcondensiup; chamber and that the ammonium chloride may when desired he also condensed. But it is lo be vfurther understood `that the condensinpr temperature may be such to condense the zinc chloride Without condensing thev ammonium chloride. As is well known in the arl. thereis sufficient difference in the volatilixingf and condensing tempera-- tures of these two chlorides to permit their separation in this manner when desired.

'lhe residue remaining` in the calcining,- furnace 22, has been found to he `practically free of all chlorine, andusually consists of a readily acid lcachabie zinc oxide, containing` or more zinc oxide. This is now leached in a leaching; cell 27 of well-known construction, with liquid containing dilute thereafter added to the electrolyte in thev electrolytic cell (not shown l used in the clectrolytic deposit ol zinc, with none oi the detrimental results previously exi'ilained.

fin the iiorm of the invention diagrammatically'illustrated in Figure 2, the flux employed in the melting retort- 10 is zinc chloride. The slag' absorbs moisture to an excessive. degree, and the screening operation ahove described is impractifal. The dross is therefore passed directly to the calcining Yiuri'iuce 2Q, and 'the process from to that detherdetailed description.

Thus it will he seen that l have provided a process for the suhstantially complete recovery ot' zinc from zinc dross with no chlorimA reni-lining in the recovered material and thus the operation of the cells to which the recovered material vmay be added is conn tinucd in the usual manner. The uX is returned to the meltingr retort, and thus the operation is cyclic. The cost of opera tion may thus greatly be reduced.

T While l have shown and described and have pointed out in the annexed claims certain novel features of my invention, it will be understood that Various omissions, substitutions and changes in the several steps of my process and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

Having thusdescrihed my invention, I claim:

l. In the art of metallurgy, the process for the recovery of valuable compounds from zinc dross, which consists in heating the dross to volatilize ythe flux residue and oxidize metallic aine carried therein.

2. In the art of metallurgy, the process for the recovery of valuable compounds from zinc dross, which consists in screening the dross, heating the screened fines, vola-- .tilizing the flux and oxidizing the carbon and metallic zinc, passing the flux and oxide of carbon to a condensing chamber and condensing' the flux therein, and subjecting the residue to a leaching,y operation.

3. In 'the art of metallurgy, the process or" treating zinc dross, which consists in heating the dross to a'red heat to volatilize the fiux and burn the carbon contained in the dross, passing the volatilized products to a condensinT 'ch-amber, condensing the linx therein, and passing the luX to a melting bath.

e. The process of' treating zinc dross to recover valuable compounds therefrom, which consists in screening the dross to separate lilies from fused particles, heating lill) the dross to a tenuoerature suilicien't to volatilize the chlorides in thel mass, oxidizing the inctalhczine and leaching the zinc oxides to recover metallic zinc as sulphate.

in the art of metallurgy, the process lfor the recovery of valuable com ounds' from Zinc dross, which consists in hearing the dross in a melting hath to sepa'rate'tl-1e volatilizahle constituents,l passing the volatilized 'product to a condensing chamber, and condcnsilner the flux and any zinc cornpounds 'formed therefrom therein, and passing the condensate to the said melting hath.

G. In the art of metallurgy, the process y of treatingr zinc dross 'which consists in screening: the dross, heating the screened* lines, collecting volatilized products there-v the hea-ted dross, collecting the said vola- /'herefrom, colecting che volatile matter, tlized prmlucts, :md cfmdensng; the Hm; and condensing the flux from the voatle 10 from the volatlized pxfmlucts, matterK i 8. The pmmss 0f troutngznc', dross *L0 ignedat Omaha in the county of @ougrecover: valuable cmnpounfls tl'lere''on'l, las and State of Nebraska this 6th day of which consists in mixing the dross with a June A. U. 1923.' I flux cmntsxnng the clement chlorine, heat- 'n in;1 the mxiuxe to Separate volatile militer JESSE OATMAN BETTERTGN. 

